Variable capacity compressor

Abstract

For a refrigerant compressor having two capacities, a camming structure operable in different manners depending on direction of crankshaft rotation, to achieve each capacity while providing top dead center piston operation thru the use of a circular cam bushing which is eccentrically, rotatably mounted on the crankshaft eccentric and within the connecting rod bearing wherein the combined eccentricities of the bushing and the eccentric equal the primary stroke of the piston. A first stop mechanism is provided for stabilizing the bushing on the eccentric upon rotation of the crankshaft in one direction whereby the eccentricities of the eccentric and bushing become aligned and remain so during synchronous rotational orbiting motion of the eccentric and bushing during rotation of the crankshaft for producing full stroke and full capacity. A second stop mechanism is provided for stabilizing the bushing within the bearing upon opposite rotation of the crankshaft whereby the bushing eccentricity becomes and remains substantially aligned with the connecting rod stroke axis while the eccentric moves alone thru its rotational orbit for producing reduced stroke and reduced capacity. A unique electrical control system is also provided for a reversible electric induction motor for selectively and efficiently driving the compressor crankshaft in either direction for providing the different capacities.

We claim: 
     
       1. A coupling structure for functionally connecting a rod bearing of a connecting rod for a piston to a crankshaft eccentric, said structure comprising: a circular cam bushing which is eccentrically, rotatably mounted on said eccentric and within said rod bearing wherein the combined eccentricities of said bushing and said eccentric equal the primary stroke of said piston;   a first stop mechanism for stabilizing said bushing on said eccentric upon rotation of said crankshaft in one direction whereby the eccentricities of said eccentric and bushing become aligned and remain so during synchronous rotational orbiting motion of said eccentric and bushing during said rotation of said crankshaft for producing a full stroke of the piston between a top dead center position and a first bottom position; and   a second stop mechanism for stabilizing said bushing within said bearing upon opposite rotation of said crankshaft whereby the bushing eccentricity becomes and remains substantially aligned with a stroke axis of said rod while said eccentric moves alone and freely rotates thru its rotational orbit for producing a reduced stroke of the piston between said top dead center position and a second bottom position above the first bottom position;   wherein said structure is configured to change the primary stroke length of the piston while effecting the top dead center position regardless of the stroke length change.   
     
     
       2. The coupling structure of claim 1 wherein said first stop mechanism comprises cooperating shoulders on said bushing and said crankshaft, and wherein said second stop mechanism comprises cooperating shoulders on said bushing and said bearing, said first and second stop mechanism becoming alternately functional upon opposite rotations of said crankshaft. 
     
     
       3. The coupling structure of claim 2 wherein said eccentricities of said bushing and said eccentric are substantially equal whereby the cylinder capacity can be switched from full to substantially one half upon reversing the crankshaft rotation. 
     
     
       4. A gas compressor having a coupling structure for functionally connecting a rod bearing of a connecting rod means to an eccentric crankpin of a crankshaft, said crankshaft being rotated by a reversible AC motor, said structure being adapted to change the primary stroke length of a piston mounted on said rod means by reversing said motor rotation while affecting primary top dead center positioning of said piston on its up stroke regardless of the stroke length change, wherein said structure comprises a circular cam bushing which is eccentrically, rotatably mounted on said crankpin and within said rod bearing wherein the combined eccentricities of said cam and said crankpin equal the primary stroke of said piston, a first stop mechanism for stabilizing said cam on said crankpin upon rotation of said crankshaft in one direction whereby the eccentricities of said crankpin and cam become aligned and remain so during synchronous rotational orbiting motion of said crankpin and cam during said rotation of said crankshaft for producing full stroke, and a second stop mechanism for stabilizing said cam within said bearing upon opposite rotation of said crankshaft whereby the cam eccentricity becomes and remains substantially aligned with a stroke axis of said rod while said crankpin moves alone and freely rotates thru its rotational orbit for producing reduced stroke. 
     
     
       5. The coupling structure of claim 1, wherein the structure is incorporated into a compressor with a reciprocating piston in a cylinder and a valve plate at the top of the cylinder and when the top dead center position of the piston is closely adjacent the valve plate, whereby the compressor operates at optimum efficiency in both the full and reduced strokes. 
     
     
       6. The coupling structure of claim 1, wherein the first stop mechanism comprises a shoulder on said crankshaft, a first pin disposed in the bushing, and a spring biasing the first pin against the crankshaft such that the first pin engages the shoulder on the crankshaft when the crankshaft rotates in the one direction and wherein the second stop mechanism comprises a shoulder on said bushing, a second pin disposed in the bearing, and a spring biasing the second pin against the bushing such that the second pin engages the shoulder on the bushing when the crankshaft rotates in the opposite direction.